1. Field of the Invention
This invention relates to a process for the production of hydrogen cyanide, and more specifically to a process wherein the reactions of methanol ammoxidation and formamide decomposition are combined simultaneously over a suitable metal oxide catalyst.
2. Description of the Prior Art
It is known in the prior art that hydrogen cyanide can be produced by the co-oxidation of ammonia and methane. More commonly known as the "Andrussow Process," the reaction can be described as: EQU CH.sub.4 +NH.sub.3 +1.5O.sub.2 .fwdarw.HCN+3 H.sub.2 O.
Despite being one of the major commercial routes to forming hydrogen cyanide, there are certain disadvantages to this process. Due to exothermicity and explosion limits of this reaction, the concentration of the reactants must be kept relatively dilute to avoid overheating the reactor which results in a low product concentration in the reactor off-gas stream. Since the off-gas stream is dilute in hydogen cyanide, large reactors and extensive downstream recovery equipment designed to handle large volumes of gas are required. Another disadvanage of this process is that the reaction must be run at high temperatures, in the range of 1000.degree. to 1200.degree. C., which are undesirable on an industrial scale, since this requires very lengthy heat-up and cool-down times. And finally there is a low ammonia conversion of typically 70% per pass, which requires recovery of the unreacted ammonia for process economy and also to avoid dangerous exothermic polymerization of the liquid hydrogen cyanide.
Other methods to produce hydrogen cyanide include the co-oxidation of ammonia with either methanol or formaldehyde over various catalysts. Suitable catalysts include antimony tetroxide, stannous oxide, and mixtures thereof, ferric molybdate, or other catalyst systems. This reaction has an advantage over the Andrussow process in that it only requires temperatures in the range of 300.degree. to 500.degree. C. to proceed. However, this reaction is also highly exothermic, and as in the Andrussow process, it requires that the concentration of rectants be kept relatively dilute to avoid overheating the reactor.
Another process for the manufacture of hydrogen cyanide involves formamide cleavage under reduced pressure and at elevated temperatures. The reaction may be written as follows: EQU HCONH.sub.2 .revreaction.HCN+H.sub.2 O.
A disavantage of this process is the endothermic nature of the reaction which requires an external source of heat to maintain the necessary reaction conditions. A further disadvantage of this process is that the reaction is equilibrium limited and therefore requires a reduced pressure (partial vacuum) to drive the reaction toward completion. The reactor off-gas then needs to be repressurized for downstream processing.